Cardiovascular 2 Flashcards
What is the arterial system
High pressure system delivering blood away from the heart
Arteries
Arteries, smallest, leading to capillary beds, blood pressure regulation
What are capillary beds
Location of exchange between blood and interstitial fluid (intercellular fluid)
What do pre capillary sphincters do
Constrict blood flow into capillary bed, protection
What is the channel that links arteries and veins (not capillaries)
Arteriovenous anastomosis
Temp regulation, get blood quickly, cart of the collateral circulation, can bypass capillaries if clotted
What do venues do
Smallest branches of veins that collect blood from the capillaries
Veins return blood back to heart
Explain blood flow through the heart
Heart
Artery
Capillaries
Venule
Vein
Heart
What are the distributions of blood volume
Systemic = 64%:
Large veins 18%
Venues and med 25%
Large venous networks 21%
Heart 7%
Pulmonary circuit 9%
Systematic arteries and capillaries 13 and 7%
What is the structure of a blood vessel
3 layers of vessel walls
- Tunica intima (inner)
Internal elastic membrane - Tunica media (smooth muscle, in arterial system)
External elastic membrane - Tunica externa
Endothelium lines lumen
Common in veins and arteries
Explain the tunica intima
Endothelial lining
Connective tissue layer
Internal elastic membrane in arteries provides elasticity to tunica intima
What does the endothelium do
Non stick
Releases vasoactive substances that affect vascular tone, blood pressure and flow
Maintains vascular homeostasis
Vasodilators - nitrate oxide
Constrictors - endothelin
Explain the tunica media
Concentric layers of smooth muscle in loose connective tissue, elastic fibres in arteries, collagen in veins
Encircles the endothelium that lines the lumen
External elastic membrane in arteries - separating from externa
Explain the tunica externa
Anchors vessels to adjacent tissues
Contains:
Collagen fibres
Elastic fibres smooth muscle cells (in veins)
What is in the walls of large arteries and veins
Vasa vasorum
- small arteries and veins in walls of large arteries and veins
- serve cells of tunica media and tunica externa
How do arteries change from the heart to the tissue
Elastic arteries - muscular arteries - arteries
E.g aorta very elastic
E.g femoral artery very muscular, less elastic
Arterioles only have smooth muscle (tunica media)
Explain the structure of capillaries
No tunica media or externa
Endothelial tube inside thin basement membrane
Continuous, fenestrated, sinusoid
No need for elastic muscle ect
What are the three types of capillaries
Continuous
Fenestrated
Sinusoid
Explain continuous capillaries
Found in all tissues except epithelia and cartilage
Have complete endothelial lining
Permit diffusion of water and solutes, block blood cells and plasma proteins
Are specialised in cns and thymus e.g blood brain barrier
Explain fenestrated capillaries
- have pores in endothelial lining
- permit rapid exchange of water and larger solutes
Found in:
- choroid process
- endocrine organs
- kidneys
- intestinal tract
Explain sinusoid capillaries
Have gaps between adjacent endothelial cells
Permit free exchange of water and large plasma proteins
Liver, spleen, bone marrow, endocrine organs
Phagocytise cells monitor blood at sinusoid
Explain capillary structure and function
Capillary beds connect a arteriole and venule
Sphincter opens and closes causing blood to flow in pulses
Thoroughfare channels, direct between arterioles and venules
Explain the structure of vein walls
Large - thicker media, more muscle and externa, extra smooth muscle
Venues, only externa
Explain venous valves
- fold of tunica intima
- prevent back flow
- compression of veins pushes blood toward heart
- varicose veins, veins near weaken, pooling
Explain skeletal muscle pump
Squeeze open the valve superior to muscle
What is Q
Total capillary blood flow = Q
Determine by pressure and resistance
Explain the role of pressure
P - pressure
- generated by heart to overcome resistance
- absolute pressure less important than pressure gradient
P gradient (change in p)
- the difference in pressure from one end of a vessel to another
Flow
- proportional to change in p / resistance
Explain peripheral resistance
Circulatory pressure must overcome total peripheral resistance (R of cv system)
Change in p across whole system about 85mmHg
Total peripheral resistance affected by
- vascular resistance, diameter of vessels
- blood viscosity
- turbulence, increases resistance
What is vascular resistance
Due to friction between blood and vessel walls
Dependent on vessel length and diameter
Length contestant, diameter changes
R up as diameter decreases
What is high and low blood pressure
Normal = 120/80
Hypertension = high, more than 140/90
Hypotension = low,
What are the cv responses to exercise
Increase hr, q, systolic blood pressure
Redistribution of blood
How much blood goes to muscles
7ml per 100g at rest, 75 during exercise
How much blood goes to muscles
7ml per 100g at rest, 75 during exercise
How is hr regulated
Parasympathetic
- via vagus nerve
- slow by inhibiting SA and AV
Sympathetic
- via cardia accelerator nerves
- stimulate sa and av
Initial increase at exercise due to parasympathetic withdrawal then sympathetic stimulation
Explain changes in sv
Increases force of contraction = increased sv
- Increases sympathetic nervous system activation, effects of adrenaline and noradrenaline- directly stimulate heart muscle
- Increased EDV lead to increased stretch of sarcomeres and increased force of contraction
What is end diastolic volume
End of diastole, volume of blood in cavities
What is the frank starling mechanism
- force of contraction proportional to fibre length
